import java.util.ArrayList;
import java.util.List;

class Solution13 {
    public  List<List<Integer>> ret;
    public  List<Integer> path;
    public  List<List<Integer>> subsets(int[] nums) {
        ret = new ArrayList<>();
        path = new ArrayList<>();
        dfs(nums,0);
        return ret;
    }

    //解法二
    public  void dfs1(int[] nums,int pos) {
        ret.add(new ArrayList<>(path));
        for(int i = pos; i < nums.length; i++) {
            path.add(nums[i]);
            dfs(nums,pos+1);
            path.remove(path.size()-1);
        }
    }

    //解法一
    public void dfs(int[] nums,int i) {
        if(i == nums.length) {
            ret.add(new ArrayList<>(path));
            return;
        }
        path.add(nums[i]);
        dfs(nums,i+1);
        path.remove(path.size()-1);
        dfs(nums,i+1);
    }

}